Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K1/00—Details of the magnetic circuit
  • H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
  • H02K1/22—Rotating parts of the magnetic circuit
  • H02K1/27—Rotor cores with permanent magnets
  • H02K1/2706—Inner rotors
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K1/00—Details of the magnetic circuit
  • H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
  • H02K1/22—Rotating parts of the magnetic circuit
  • H02K1/27—Rotor cores with permanent magnets
  • H02K1/2706—Inner rotors
  • H02K1/272—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis
  • H02K1/274—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis the rotor consisting of two or more circumferentially positioned magnets
  • H02K1/2753—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis the rotor consisting of two or more circumferentially positioned magnets the rotor consisting of magnets or groups of magnets arranged with alternating polarity
  • H02K1/276—Magnets embedded in the magnetic core, e.g. interior permanent magnets [IPM]
  • H02K1/2766—Magnets embedded in the magnetic core, e.g. interior permanent magnets [IPM] having a flux concentration effect
  • H02K1/2773—Magnets embedded in the magnetic core, e.g. interior permanent magnets [IPM] having a flux concentration effect consisting of tangentially magnetized radial magnets
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K21/00—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets
  • H02K21/12—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets with stationary armatures and rotating magnets
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K2213/00—Specific aspects, not otherwise provided for and not covered by codes H02K2201/00 - H02K2211/00
  • H02K2213/03—Machines characterised by numerical values, ranges, mathematical expressions or similar information

Definitions

• the present invention relates to a permanent magnet rotor for a rotating electrical machine.
• the invention also relates to a rotary electric machine comprising a rotor of this type, in particular for applications in the field of motor vehicles.
• “Mild-hybrid” applications generally concern electrical machines of the order of 8 to 10 KW, for example, an electric motor mounted on the front face of a heat engine and coupled thereto by a transmission belt. It is possible with such an electric motor to reduce the displacement of the engine (“engine downsizing" in English terminology) by providing a power assisted torque that provides additional power, especially during rework. In addition, a low-speed traction, for example in urban environment, can also be provided by the same electric motor.
• Another example of application of electrical machines of this power range is the drive of a centrifugal compressor of a double supercharging system of a heat engine.
• the electric compressor assists at low revs turbo-compressor driven by the exhaust and allows to take a step further in the reduction of the engine.
• “Full-hybrid” type applications generally concern motors from 30 to 50 kW for series and / or parallel architectures with a level more advanced integration of the electric motor (s) in the vehicle's drivetrain.
• Neodymium-Iron-Bore Neodymium-Iron-Bore
• SmFe Samarium-Iron
• SmCo Samarium-Cobalt
• rare earth magnets in an electric machine rotor for automotive applications are no longer economically viable, and probably not sustainable, the other term of the alternative is constituted by magnets based on ferrites.
• the object of the present invention is therefore to optimize the shape of the poles of a rotor to maximize the magnetic flux in the poles and thus preserve the torque of the machine. It relates specifically to a rotary electric machine rotor comprising a plurality of alternating North poles and South poles and formed from a plurality of permanent magnets arranged in first recesses.
• first recesses extend along an axis of the rotor and are regularly distributed between a circumferential portion and a central portion of the rotor magnetic mass so as to define a plurality of circumferential pole sections.
• the permanent magnets of the rotor type in question have a first polygonal radial section and a first plane of axial symmetry.
• the circumferential portion comprises, in turn, axial grooves which are arranged between the polar sections opposite the permanent magnets and which form opening of the first recesses.
• the rotor according to the invention is remarkable in that this opening has a first predetermined width so as to make minimum a leakage magnetic flux circulating in a circumferential direction in the circumferential part and to make maximum a useful magnetic flux circulating radially in each of the polar sections, this circumferential portion has a predetermined opening ratio so as to minimize the leakage magnetic flux and to maximize the useful magnetic flux, this opening ratio being equal to a first ratio of the first width of the opening to a second width of the permanent magnets in a circumferential direction and this opening ratio is substantially between 0.35 and 0.8.
• the rotor according to the invention is also remarkable in that the first radial section of the permanent magnets has a rectangular portion close to the circumferential portion adjacent to a wedge-shaped portion near the central portion.
• the rotor according to the invention further comprises at least a plurality of second recesses which extend axially and which are arranged between the permanent magnets in an intermediate portion of the rotor between the central portion and the circumferential portion.
• Non-magnetic tie rods are preferably arranged in these second recesses.
• the polar sections also advantageously have a second radial section forming an outer lobe and a second plane of axial symmetry.
• a second ratio of the second width of the magnets to a sum of the first width of the opening and a third width of the lobe, in the circumferential direction, substantially between 0.25 and 0.6 preferably characterizes the rotor in this variant.
• the permanent magnets of the rotary electric machine rotor according to the invention are made of ferrite.
• the invention also relates to a rotating electrical machine which comprises a rotor having the above characteristics.
• Figure 1 shows a simplified radial sectional view of a rotor with permanent magnets in a main embodiment of the invention, arranged in a stator, shown in partial radial section, of a rotary electric machine according to the invention.
• Figure 2 shows a simplified model of the influence of the opening grooves of the circumferential portion of the rotor on the flow of magnetic flux in the rotor according to the invention.
• Figure 3 shows the relative variation of the useful flux in the vicinity of a maximum useful flux as a function of the opening ratio obtained by the simplified model shown in Figure 2.
• FIG. 4 shows the absolute and relative variations, in the vicinity of a maximum, of the electromotive force constant between phases as a function of the opening ratio obtained by a computer simulation of a complete machine comprising a rotor according to the mode of embodiment shown in Figure 1.
• FIG. 5 shows a simplified radial sectional view of a permanent magnet rotor according to an alternative embodiment of the invention, arranged in a stator, shown in partial radial section, of a rotary electric machine according to the invention.
• FIGS. 6a and 6b respectively show the waveform of the electromotive force between no-load phases and the corresponding harmonic levels of a rotary electric machine comprising a rotor according to the embodiment variant of the invention shown in FIG. .
• FIGS. 7a and 7b respectively show the waveform of the electromotive force between empty phases and the corresponding harmonic levels of a rotary electric machine of the type of that shown in FIG. 5 but whose circumferential portion of the rotor does not would not include opening-forming grooves.
• the rotor 1 according to the invention is of the flux concentration type.
• the permanent magnets 3 are generally of substantially rectangular section, but chamfered in the shape of a wedge towards the axis X-X 'of the rotor 1. They extend symmetrically in the vicinity of equiangular axial planes.
• the first recesses 4 in which the permanent magnets 3 are arranged delimit ten polar sections 7 circumferential.
• the circumferential portion 5 has axial grooves 8 which are arranged between the polar sections 7 facing the permanent magnets 3 and which form the opening of the first recesses 4.
• the pole sections 7 comprise second recesses 9 arranged between the permanent magnets 3. They extend symmetrically in the vicinity of equiangular axial planes.
• These second recesses 9 have a circular section and receive non-magnetic tie rods holding the metal sheet packets forming magnetic masses 2, 10 of the rotor 1 and a stator January 1.
• the rotor 1 comprising ten permanent magnets 3 rotates inside a stator January 1 having a plurality of notches 12 defining a plurality of stator teeth 13 around which are arranged stator windings 14
• a concrete embodiment of a machine comprising such a rotor 1 is for example a motor / generator of 8 to 10 KW for applications in motor vehicles of the type called "mild-hybrid".
• this machine In its motor mode of operation this machine can be designed for starting the engine, assisting the engine in torque, electric traction at low speed of the vehicle as well as for driving a centrifugal compressor.
• the stator windings 14 are traversed by a stator current and create a rotating magnetic field driving the rotor 1.
• the engine torque supplied depends in particular on the intensity of the stator current and the magnetic flux in the rotor 1.
• the replacement of permanent magnets 3 with rare earths by ferrite permanent magnets 3 requires optimization of the magnetic poles N, S to obtain a similar magnetic flux in the rotor 1, and thus to preserve the same motor torque for the same stator intensity.
• the magnetic leakage flux OL depends on the first width a of the opening 8 of the recesses 4 containing the permanent magnets 3. The greater this first width a, the more the magnetic leakage flux OL decreases because a first reluctance at this location of the circumferential portion 5 increases, but the useful magnetic flux OR also decreases because a surface of a pole N, S facing a stator tooth 13 decreases. There is therefore a first optimal width of the opening 8, which is determined by the simulation, for which the magnetic leakage flux is minimum and the useful magnetic flux OR is maximum.
• the variations of the first width a of the opening 8 are related to the variations of an opening ratio g equal to a ratio of the first width a to a second width w of the permanent magnets 3. In this way, this ratio g varies of 0, when the first recesses 4 are completely open towards the outside, at 1, when these first recesses 4 are completely closed.
• the first reluctance results from the sum of the reluctances of a first segment 8 of the circumferential portion 5 of the rotor 1 of a first length equal to g, having a first relative permeability ⁇ (equal to that of the air), and of a second segment 5 of a second length 1 - g, a second relative permeability ⁇ 1 is that of the first carcass 2 of the rotor 1.
• the first and second segments 8, 5 have a thickness e with w as a unit.
• a second reluctance involved in this simplified model is that of a magnetic circuit, in which the useful magnetic flux OR flows between the poles N, S of the rotor 1 and the stator teeth 13 of the stator January 1, having a third length Lst, and a third relative permeability ⁇ 2 is that of a second carcass 10 of the stator 1 1.
• Figure 3 shows the relative variation of the magnetic flux utMe near the maximum OR max as a function of g.
• the magnetic flux increases when the opening ratio g is up to 0.80.
• a more realistic computer simulation of a rotating electrical machine comprising a rotor 1 according to the invention confirms the existence of a maximum of the useful flux OR for a value of the opening ratio g substantially equal to 0.8, as the shows Figure 4.
• This figure shows the evolution of the electromotive force constant between phases Ke for values of the opening ratio g substantially between 0.3 and 0.9.
• Ke is representative of the useful magnetic flux OR. It is noted that it increases to reach a maximum towards an opening ratio g of the order of 0.8.
• the optimized structure of rotor 1 contributes to the preservation of machine performance when ferrites are used instead of rare earth magnets, without increasing the mass of permanent magnets 3.
• the possibilities of optimizing the useful magnetic flux OR in the main embodiment of the invention described above, by playing on the first width a of the opening of the first recesses 4, are limited by the fact that the circumferential pole sections 7 have a third width p which tends to decrease when a increases, causing a rapid increase in the second reluctance of the magnetic circuit between the poles N, S of the rotor 1 and the stator teeth 13 of the stator January 1.
• the pole sections 7 have a second radial lobe section 15.
• the partial overlap of the permanent magnets 3 by the lobes 15 at the periphery of the rotor 1 increases the thickness of the circumferential portion 5 (the dashed line in Figure 5 shows the outer surface of the rotor in the main mode of realization), and contributes to attenuate the increase in the second reluctance of the magnetic rotor 1 - stator 1 1 as the opening ratio g increases, that is to say, contributes to maximize the magnetic flux of all and minimizes the magnetic flux leakage ⁇ _.
• the inventive entity has determined that a second ratio of the second width w of the permanent magnets 3 to a sum of the first width a of the opening 8 and the third width p of the lobe substantially between 0.25 and 0.6 is optimal.
• the advantage of this variant is a magnetic noise generated by the reduced machine due to the reduction of the harmonic distortions of the electromotive force and the torque, as shown in Figures 6a and 6b.
• a waveform 17 of the electromotive force between phases U1 ph-ph vacuum of a machine comprising a rotor 1 according to this variant appears as substantially sinusoidal in Figure 6a.
• Figures 7a and 7b show the same characteristics corresponding to a rotating electrical machine (not shown) of the type shown in Figure 5 but the circumferential portion 5 of the rotor 1 would not include opening grooves 8.
• FIG. 7b confirms that a 5th rank harmonic having an amplitude representing more than 6% of the fundamental harmonic 18 is present in this case, whereas it did not exist for the machine comprising a rotor 1 according to the variant of FIG. realization ( Figure 5).

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Permanent Field Magnets Of Synchronous Machinery (AREA)
• Iron Core Of Rotating Electric Machines (AREA)
• Permanent Magnet Type Synchronous Machine (AREA)

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• 2011
  • 2011-12-01 FR FR1161019A patent/FR2983658B1/fr active Active
• 2012
  • 2012-11-06 US US14/362,367 patent/US9641031B2/en active Active
  • 2012-11-06 WO PCT/FR2012/052564 patent/WO2013079842A2/fr not_active Ceased
  • 2012-11-06 EP EP12794448.6A patent/EP2786470B1/de active Active
  • 2012-11-06 CN CN201280059590.4A patent/CN103988400B/zh active Active
  • 2012-11-06 JP JP2014543951A patent/JP2015503318A/ja active Pending

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